Electronic apparatus



,May 24, 1949.

1.. 0. SMITH 2,471,246

ELECTRONIC APPARATUS Filed May 25, 1944 llllll CENTERING CONTROL\NTENSITY CAT HODE.

TO CON 0L AAAAAA INVEN TOR. L. c. smm-u.

ATTORNEY Patented May 24, 1949 2,471,246 ELECTRONIC APPARATUS Lester C.'Smith,

of Delaware Westmont, N. J., assignor to Radio Corporation of America,

a corporation Application May 25, 1944, Serial No. 537,275

10 .Claims.

The present invention relates to an improvement in cathode rayOscilloscopes, and more particularly to-oscilloscopes"wherein singlesweep deflection provisions are present.

'-In U. S. patent application entitled Deflection circuits flled by thisapplicant concurrently-herewith as Serial'No. 53-'7',2'75, issuedDecember 10, 1946, as Patent No. 2,412,542, a circuit arrangementisshownand described wherein voltage variations be used for deflecting acathode ray beam in -a-cathode ray oscill'oscope. The circuitarrangement 'is of such a nature that the cathode ray beam may -bede'flected across the screen of the viewing tube each be observed isapplied thereto, the beam bein normally maintained :in a staticcondition in the absence \of :such transient conditions. By "means :ofthe circuit arrangement, single sweep deflections of a cathode ray beammay be produced.

Since transient phenomena do not, in most instances, :occur at regularintervals, single sweep provisions must be made :in order that anapparently stationary trace may be produced on the screen or rta'rgetarea of the :cathode ray tube 'used it)! :observation purposes. In someinstances, it is possiblerthata transient phenomena :may .OCCllIliIlrelatively widely spaced time :intervals, whereas in other instances thesame transient phenomena may-occur in rather rapid succession. If ;a:single sweep deflection geniera'tor is -usedawhich will respond to eachtransient condition, then the horizontal deflection aOf theucathoderay,=beam, in the oscilloscope will be deflected-,atsuch intervals whenthe transient condition :occurs, with :the result that the horiizontaldeflections oi the cathode :ray beam may ioccur during rather spacedintervals or the .sweep deflection may ;be produced in relatively .rapidsuccessionzover. afperiodof time. By reason -;of this inconsistencyinthe :frequency of occurrence of the transient phenomena and theresultant inconsistency in the repetition frequency of the cathode:raybeamz-sweep deflections, certainlundesirablereffects will result ina conventional deflection amplifier and in the circuits associated withthe cathode .ray tube which will acause a change in-lthe biasing orstatic conditions present in the circuit.

More specifically, :in' cathode ray oscilloscopes a provisionris .madewhereby the hori- :.zontal :position of .a cathode :ray beam as welllras'the area traversedzby thexbeam'duringits hori- Isontaldeflectionimayube controlled manually are developed which may time .atransient signal to w I for centering purposes. applies a predeterminedstatic bias to the de- This centering control fleeting plates of thecathode ray tube so that when the sweep deflection potentials (ofproperly adjusted intensity) are superimposed :thereon, the cathode .raybeam will be deflected between predetermined prescribed limits and overa predetermined portion of the viewing screen. It is naturally desirablethat this predetermined bias potential that is applied to the.deflecting plates of the :cathtode ray tube remain substantiallyunchanged (unless a change is deliberately made) since any change in thebiasing potentials applied to the plates will cause a shifting of the:area transversed by the beam during its deflections.

Due to the nature of circuit arrangements usually associated with.cathode ray tube tin toscilloscopes, when the sweep deflection rates arerapidly varied a.gradual change in the average potential ofthe-deflecting plates takes place, with the result that after a seriesof rapidly successive deflections, the .area traversed by the cathoderay beam may shift in one direction or another and the produced image isaccordingly shifted. iSuch an operation is undesirable since it ispreferable that the produced image or trace remain apparentlystationary.

The same or a-similar situation exists in re- ;gard to a deflectionamplifier tubes that are associated with the deflection plates of thecathode ray tubes.

A purpose of the present invention, therefore,

resides in the provision of means in a cathode ray oscilloscope wherebythe deflection potentials :applied to the cathode ray beam aremaintained within the desired range regardless of the frequency at whichthe cathode ray beam is deflected across the screen of the viewing tube.

Another purpose of the present invention resides in the provision ofmeans in a cathode ray oscilloscope wherein single stroke deflectionprovisions are available whereby the area or .region traversed by :thecathode ray beam during its sweep deflections remains unchangedregardless of whether the deflections are widely separated in point .oftime or whether they occur in rapid succession.

Still another purpose of the present invention resides in the provisionof means whereby the centering or bias potential applied to thedeflecting electrodes of a cathode ray oscilloscope will remain withinthe desired range regardless of the particular superimposed deflectionvoltages applied therefore.

A still further purpose of the present invention resides in theprovision of means in a deflection amplifier for a cathode rayoscilloscope whereby the bias potential applied to the deflectionamplifier tubes remains within the desired range regardless of the waveform of the applied voltage variations.

Other purposes and advantages of the present invention will become moreapparent to those skilled in the art from the following detaileddescription wherein:

Figure 1 represents a preferred form of the present invention: and

Figure 2 shows a curve used in explaining the operation of the system.

Referring now to the drawing, a pair of defiection tubes and are usedfor causing horizontal deflections of the cathode ray beam. These tubeseach include a cathode, a control electrode and an anode. The cathode l2of tube It and the cathode 22 of tube 20 are connected together, and areconnected to ground or a source of fixed potential by means of a seriesarrangement of resistances 32, 34, 36 and 33.

The control electrode M of tube it? is connected to input terminal 40 byway of coupling condenser 42 and a relatively small oscillationsuppression resistance 44. A grid resistance 33 is connected to extendbetween the junction of the coupling condenser 42 and the resistance i land the junction of resistances 32 and 3d. This connection afiords acertain amount of self bias for tube H], the extent of the bias beingdetermined by the combined resistance of the re sistance elements 34, 36and 38.

The control electrode 24 of tube 23 is connected to the junction ofresistances 3i; and 38 by means of a relatively small oscillation supression resistance 48 and grid resistance 56. This connection affords abias between the oathode 22 and. control electrode 24 of tube 23 in anamount determined by the potential drop across resistance 38. Thejunction of the resistance 38 and the grid resistance 50 is connected toground by means of a relatively large condenser 52.

The anodes It and 26, respectively of tubes ill and 23 are connected, byway of a load circuit, to terminal 54 to which a source of positivepotential is applied. Each anode load circuit in. cludes a loadresistance 56 and may include a peaking coil or inductance 58. Voltagevariations present at the anodes l6 and 23 of the deflection tubes I 3and 20 may then be applied to the horizontal deflecting plates of acathode ray tube.

In the circuit arrangement so far described, tubes l3 and 20 affordcathode ray beam deflection potentials in an out-of-phase relationshipso that a push-pull action may result. Only a single input is providedat terminal it, and by reason of the circuit arrangement associated withtubes l3 and 29, a phase inversion or pushpull operation isaccomplished. It will be noticed that the bias potential applied tocontrol electrode I 4 relative to the cathode i2 is determined by thepotential drop across the three series resistances 34, 36 and 38,whereas the bias potential applied to the control electrode 23 relativeto cathode 22 is determined by the voltage drop across resistance 38only. By proper choice of the relative size of these resistances, thetubes l0 and 20 may be biased at different static conditions.

It will also be observed that the control electrode 24 is efiectivelyconnected to ground ins0- far as an alternating current component is concerned by means of relative large condenser 52. This precludes anymodulation of the potential applied to the control electrode 24. Theinput potentials which are applied to the terminal to are impressed uponthe control electrode 54 of tube Hi and the electron stream in tube 23is subjected to cathode modulation.

Referring now to Figure 2, there is shown a curve representing theplate-current/grid-potential characteristic of tubes l0 and 28, and theresistances 34, 36 and 38 are so chosen that the normal bias appliedbetween the control electrode and cathode of tube I0 is of a valuesimilar to that, for example, represented by the dotted line E10 ofFigure 2. Furthermore, since only the voltage drop across resistance 33is utilized in biasing the control electrode 24 of tube 251 relative toits cathode, the bias potential on tube 28 will be materially less thanthat applied to tube It! and the value of resistance 38 is chosen suchthat this bias potential will be approximately as represented by thedotted line E20 of Figure 2, indicating a rather low bias condition.

With this arrangement, when signals or voltage variations extending in apositive direction, such as represented by curve 60, are applied to theinput terminal 40, the potential of the con trol electrode I4- ismodulated in a positive direction relative to the cathode l'2 whichreduces the bias applied to tube IE], and accordingly increases theamount of current permitted to pass through the anode circuit of tubeI0. This increased current causes a fluctuation in the potential of thecathodes l2 and 22 in a corresponding positive direction so that thecathode 22 of tube 29 is modulated in a positive direction, whichresults in a reduction in the amount of current permitted to flow in theanode circuit of tube 20.

The application of positive impulses or voltage variations to the inputterminal 49, therefore, results in momentary increases in the currentpermitted to flow in the anode circuit of tube ill and correspondingmomentary decreases in the current permitted to flow in the anodecircuit of tube 20. These momentary increases and decreases in currentin the two anode circuits produce, respectively, corresponding negativeand positive potential variations in the anode circuits of the twotubes, as indicated by the curves Gill and 632. A push-pull deflectionaction is, therefore, produced although only a single input is provided.

Referring again to Figure 2, it will be seen, therefore, that the biaspotential on tube It is normally that represented by E10 and the biaspotential on tube 20 is normally that represented by E20. When signalpotentials extending in a positive direction are applied to the inputterminal, the bias potential applied to tube I l is decreased from thevalue represented by the dotted line E10 and simultaneously the biaspotential of tube 20 is increased from the value represented by thedotted line E20.

Figure 1 also shows a portion of a cathode ray tube 62 which includeshorizontal deflecting plates 64 and 66, as well as a pair of vertical defleeting plates 68. The signal to be observed is naturally applied tothe vertical deflecting plates 68, and since such circuit arrangementsare well known to those skilled in the art no provision is indicated forapplying a transient signal or other voltage variation to be observed tothe vertical deflecting plates. The horizontal the secondanode ablecontact of potentiometer 90 in order to afford a focus control, and

. Stand 96 is connected to:

cting plate 64, is connected to the anode H or deflection tube H) bymeans of a coupling conde ser 10. A series connected peaking induct-;anoe 12' may be included in the circuit and the 'may be effectivelyapplied to the horizontal defleetin Plates 64 and as.

" For reasons ofsimplicity the electron gun structure of the cathode raytube 62, is not shown, but as is the usual custom, negative potentialsmay be applied to the cathode and control electrode of the electron, gunstructure, relative to the gun anode in order that a desired cathode maybe generated. The highvol-tage negative poray beam tential may beconnected to terminal 82- with the associated-positive potentialconnected to the terminal: 84. Between these two terminals is connectedthe usual bleeder resistances including potentiometer g6, resistance 88,potentiometer 9t,

resistance 92-, andparal-lelly connected centering 'potentiometers 94and 96.

The cathode of th electron gun structure may be connected to thejunction of-resistances 86 and 88, as indicated in the drawing, in whichcase the control electrode would be connected to a movable contact of'potentiometer 86. Similarly,

would be connected to the movthe first anode of the cathode ray tube maybe connected to ground or to a potential approximating that applied tothe terminal 84.

Due to the current flowing through this series of resistances includingthe centering controls 94 and 96, the potential along the potentiometersvariable and the adjustable contact associated with each of thesepotcntiometers is the deflection plates 6,4 and 66 by 'way of relativelyhigh resistances 98 and IjOil, re-

spectively. By an adjustment of the position of the movable contactsalong potentiometers 94 and 96-, a horizontal adjustment of thepositionof the cathode ray beam is made possible.

Preferably the two centering controls, i. e., the movable contactsassociated with potentiometers 9 4 andjfifi are ganged. together forsimultaneous operation. Such a procedure is well known to those skilledin the art. The movable contacts associated with, these centeringpotentiometers are connected to ground by way of condensers I02 and IMin order to preclude the possibility of any possible rapid, potentialfluctuations on the potentiometers from reaching the deflectingelecrodes- "I hecircuitarrangement as so far described affords a, meansfor causing deflections of a cathode ray beam, the deflecting potentialsbein applied to the deflecting electrodes in. a push pull manner inresponse to the application of a single voltage variation toinputterminal 40. If the cathode ray oscilloscope is to be used, in, aconventional manner where the deflection potentials are regularlyrecurrent at a predetermined rate determined. by thev frequency ofoperation of the deflection generator, the cathode ray beam will bedeflected repea dly n. a orizontal direction.

f: the eflection. voltage. variations. ecapplied to treinputterminalmll: arenot regularly recurrent but are derived from asingle sweep deflection generator, then, under certain conditions,certain undesired efiects will take place. For example, the bias E10normally present between control electrode and cathode of tube I0. isdetermined by the voltage drop across resistances 34, 36. and 38. Thisbias is applied to the control electrode by way of grid resistance 46,and a coupling condenser 42 is included between the input terminal 41]and the grid end of the grid resistance. 4:6,.

Suppose, for example, that no deflection voltage variations are appliedto the input terminal, then the static bias condition will, of course,

,prevail on tubes lit and 20. If a recurrent transient condition occurs,then for each transient condition a deflection voltage variationextending in a positive direction will be applied to the input terminalMl from the. single sweep. deflection generator (an example of which isshown and described in the above mentioned L. C. Smith application).These deflection voltage variations may occur at rather widely spacedintervals or they may occur in relatively rapid succession. Thedeflection voltage variations, as applied to input terminal All, extendin a positive direction to modulate the control electrode IA of tube 10in a positive direction from its normal static bias potential E10 ofFigure 2. If the individual single sweep deflection voltage variationsare widely separated in time, then the modulation of the controlelectrode M will. be in a positive direction and very little or nodistortion will result.

If, however, a series of rapid or closely spaced deflection voltagevariations are applied to the input terminal 40, after a few cycles thealternating current axis will shift (due to the presence of condenser42) with the result that the voltage swing in a negative direction fromE 10 will become appreciable and may in fact approach the swing inpositive direction from E10. Such a conditiOn is undesirable sinceappreciable potential, changes in a negative direction from Em woulddrive. the control electrode potential of tube [0 beyond cutoff andresult in serious diSlEOr iO 0 the defl ction wave form.

In order to overcome this undesirable operation some provision must bemade to prevent excessive excursions of the control electrode IA of tubeIt) in a negative direction fromlilio, regardless of the wave form orcharacteristics of the input signal. For this purpose the diode it isincluded in. the circuit as described above. The diode is connectedacross grid resistance 46 so that any potential change of the controlelectrode l=4 in= a direction appreciably negative with respect to thepotential E10 causes the cathode of the diode M0 to become negative withrespect to its anode with the result that the diode becomes conductive.Due to the conduction of the diode I I0 a potential is produced acrossresistance 46 thus causing a charge to accumulate on condenser 42 whichdisplaces the average potential of the control electrode M in a positivedirection withv the result that the control electrode is never driven ina negative direction from potential E10 by any appreciable extent.Accordingly, distortion is prevented and the control electrodemodulations are always in a positive direction with respect to potentialE10 regardless of the frequency of occurrence of the sweep deflectionpotential variations to input terminal 4:0.

For similar reasons, and in the absence of the diode I20, it is possiblefor the control electrode 24 of tube 20 to be effectively modulated byasubstantial amount in a direction positive with respect to thepotential E20. Since it is desired that the potential difference betweenthe control electrode 24 and the cathode 22 of tube 20 be confinedprimarily to the region between E20 and E10, a diode I20 is included inparallel with the grid resistor 56. The operation of this diode upon thepresence of a series of closely spaced deflection potential variationsis similar to the operation of the diode I I and results in precludingany appreciable effective modulations of the control electrode 24 in adirection positive with respect to the potential E20. Actually themodulation of the electron stream in tube is by cathode modulation whilethe undesired operation is prevented by a change in the potential of thecontrol electrode by reason of the operation of diode I20. The applieddeflection wave form will, therefore, be amplified without distortionregardless of the frequency of occurrence of the sweep deflectionvoltage variations.

When diodes H0 and I20 are included in the circuit it is possible,therefore, to apply sweep voltage variations to tubes I0 and 20 wheresuch voltage variations are subjected to amplification, and the degreeof amplification remains constant and without appreciable orobjectionable distortion regardless of the rate or frequency at whichthe voltage variations are applied and regardless of the rate at whichtheir frequency of application varies. Amplified deflection voltagevariations are then present at the anodes of tubes I0 and 20 and at thecoupling condensers '10 and 16.

These deflection voltage variations are applied to the horizontaldeflecting plates 64 and 66 of the cathode ray tube 62.

Since the sweep voltage variations may be rather widely separated orclosely spaced in point of time, a change in the position (average) ofthe trace on the screen of the cathode ray tube may occur by reason of ashift in the alternating current axis of the voltage variations presentat the coupling condensers I0 and 16. If the alternating current axisshifts appreciably, as when a rapid succession of deflection voltagevariations occur, the produced trace will gradually shift horizontallyacross the screen and such shifting is, of course, objectionable.

In order to preclude a horizontal shifting of the position of the traceon the cathode ray oscilloscope tube, diodes I and I26 are employed andthese are effectively connected in parallel with resistances 98 and I00,respectively. The anode of diode i 2 2 is connected to the cathode raybeam deflection plate 64, i. e., to the end of the resistance 98 whichis subjected to the deflection voltage variation. The cathode of diodeI24 is connected to the centering control end of resistance 98, whichpoint in the circuit is effectively connected to ground, insofar as anyalternating current component is concerned, by reason of the inclusionof condenser I02.

The diode I26 is poled in an opposite manner since the undesired changein potential of the conductor connected to the deflecting plate 65 is ina direction opposite to that which occurs in connection with the otherdeflecting plate. In this case, the cathode of the diode I26 isconnected to beam deflection plate 66 and to the end of resistance I 06that is subjected to full deflection potential variations. The anode ofthe diode I26 is connected to the centering control end of resistance1106, which point in the circuit is effectively connected to ground,insofar as any alternating current component is concerned, by reason ofthe inclusion of the condenser I04.

As explained above, under static conditions the potential at thecoupling condenser 10 and at the deflecting electrode 64 is maintainedat a predetermined value. When a series of deflection voltage variationsare successively transmitted through the circuit the alternating currentaxis of the voltage variations present at coupling condenser I0 shiftsand after a few cycles the potential deviations as applied to thedeflecting electrode 64 will become effective on both sides of thenormal average potential of the electrode I54v with the result that thenegative peaks will not cause as great a deflection of the beam from theelectrode 64 and the positive portion of the deflection voltagevariations will, in fact, cause the beam to be attracted nearer theelectrode 64 resulting in a shift of the trace toward the left acrossthe screen. It is desired that the deflection voltage variations cause arepulsion only of the beam and that these variations do not extend in adirection appreciably positive with respect to the normal bias potentialof electrode 64.

When diode I2 5 is included in the circuit as described above, anyvariation of the potential of electrode 6% in a direction positive withrespect to the normal bias potential determined by potentiometer :3causes the diode to conduct which results in the production of apotential drop across resistance 98. The end of the resistance adjacentcoupling condenser I0 becoming negative with respect to the other end sothat the tendency for the trace to shift is compensated. This change inpotential of the end of resistance 98 may be looked upon as resulting ina change in the average potential of the deflecting electrode 64 in anegative direction by an amount corresponding to the shift in thealternating current axis so that the potential deviations of electrode64 may always extend in a negative direction from the normal staticpotential of electrode fill with Very little or no deviation inpotential in a positive direction from that static potential value. Byreason of the diode I 24, the trace remains in a fixed position and doesnot shift horizontally regardless of the rate or change in rate at whichthe deflection voltage variations are applied.

Similarly, diode I26 prevents a similar effect from taking place withrespect to deflecting electrode 6B. This diode is poled oppositely withrespect to diode I24 since the deflection voltage variations present atcoupling condenser I6 are in push-pull relation to those at condenserI0. Diode I25, therefore, produces a potential across resistance we sothat the potential deviations of electrode 66 are always in a directionpositive with respect to the normal static bias potential of theelectrode regardless of the wave form applied thereto.

By reason of the present invention, it is possible to apply single sweepdeflection potentials to the deflecting circuit amplifier and to thedeflecting plates of a cathode ray tube at any desired rate and in anywave form without in any Way affecting the operation of the system. Theinclusion of the diodes II 0 and I20 prevents a shift in the gridmodulation range of tubes I0 and 2d, and the inclusion of the diodes I24 and IE6 prevents a shift of the oscillographic trace on the screen ofthe cathode ray tube. It is,

therefore, immaterial whether the deflecting potential variations occurin regular sequence and, in fact, a Wide deviation in the rate ofapplication of the deflection potentials to the circuit is entirelypossible without affecting the operating characteristics of tubes I0 and20 and without causing 'anyshift whatever in thehorizontalrpositioniri'g oilthe trace on the screen of the cathoderaybscilloscope tube.

Although the have tion is described more or less in detail, and althoughpush-pull operation is shown,- asingle amplifier may also be used inwhichthe present invention is employed and the deflectingv potentialsmay be applied to one plate only of the horizontal deflecting plates.Furthermore, the present invention may be applied to any type amplifierwhere a similar situation exists and need not be confined tooscilloscope use.

Various other alterations and modifications may bemade therein withoutdeparting from the spirit and scope thereof, and it is desired that anyand all such alterations and modifications be-considered within thepurview of the present invention, except as limited by the hereinafterappended claims. I

Having now described the invention, what is claimed is: I v

1. A cathode ray oscilloscope including an amplifier tube having acathode, a control electrode and an anode, means for applying apredetermined static bias potential between the control electrode andthe cathode of said tube, condenser means for applying voltagevariations extending in a predetermined potential direction and ofvarying wave form to the control electrode of said tube, a unilateralconducting device associated with the co trol electrode of said tubetoconfine the operation of the tube to a predetermined portion of itsoperating characteristic so that amplified voltage variations arepresent at the anode of said tube, a cathode ray tube lncludinga pair ofcathode ray beam deflecting electrodes, means for applying apredetermined static bias potential to one of the deflecting electrodesrelative to a point of fiXcd potential, condenser means for applying theamplified voltage variations to the said one deflecting electrode, andmeans including a unilateral conducting device for preventing a shift inthe area traversed-by the deflected cathode ray beam by reason ofchanges in the wave form of the applied voltage variations.

2. A cathode ray oscilloscope including an amplifier tube having acathode, a control electrode and an anode, -xrieans for applying apredetermined static bi'as potential between the control electrode andthe cathode or said tube, means for applying voltage variations ofvarying wave form to the control electrode of said tube, a unilateralconducting device included in the control electrode circuit of said tubeto confine the potential variations of the control electrode of the tubeto a predetermined potential direction from the bias potential so thatconsistently uniformly amplified voltage variations are present at theanode of said tube, a cathode ray tube including a pair of cathode raybeam deflecting electrodes, means including a resistance for applying apredetermined static bias potential to one of the electrodes relative toa point of fixed potential, means for applying the amplified voltagevariations to the said one deflecting electrode, and means including aunilateral conducting device connected in parallel with said resistancefor preventing any alteration in the area traversed by the deflectedcathode ray beam by reason of changes in the wave form of the appliedvoltage variations.

3. A cathode ray oscilloscope including an amplifier tube having acathode, a control electrode variations are present at with eachresistance for sition of the beam,

and an anode, means including a resistance for applying a predeterminedstatic bias potential between the control electrode and the cathode offor applying voltage variations.

said tube, means to the control electrode of said tube, a unilateralconducting device connected in parallel with said resistance to confinethe operation of the tube to a predetermined portion of its operatingcharacteristic regardless of the wave form of the applied voltagevariations so that amplified voltage the anode of said tube, a cathoderay tube including a pair of cathode ray beam deflecting electrodes,means including a second resistance for connecting one of the.defleeting electrodes to a point of fixed potential,- means for applyingthe amplified voltage variations to the said one deflecting electrode,and means including a diode connected in parallel with said secondresistance in the deflection limits of the ray beam by reason of changesin the wave form and the applied voltage variations.

4. A cathode ray oscilloscope apparatus in-.

cluding a push-pull deflection amplifier comprising two tubes eachincluding a cathode, a control electrode and an anode, means forconnecting the cathodes of the two tubes together, means including aresistance to connect the cathodes to a point of fixed potential, afirst grid resistor connecting the control electrode of one of the tubesto one point along said resistance, a second grid resistor connectingthe control electrode of the other of the tubes to another point alongsaid resistance, whereby a difierent bias potential is maintained on thetwo tubes, means to apply modulating voltage variations of variable waveform to the control electrode of one of the tubes to thereby modulatethe bias potential of the tubes in a push-pull manner and in oppositedirections by the voltage variations, and means to confine the potentialmodulation to a predetermined deviation range relative to the biaspotential of each tube regardless of the Wave form of the appliedvoltage variations, said lastnamed means including a unidirectionalcurrent conducting device connected across a portion of the resistor inthe control electrode circuit of each of the amplifier tubes.

5. A cathode ray oscilloscope including a cathode ray tube having a pairof cooperating defiecting electrodes for deflecting the cathode ray beamin a predetermined plane, means for applying a predetermined static biaspotential to the deflecting electrodes to determine the static pomeansfor applying a deflection voltage variation in push-pull relationship tothe deflecting electrodes in order to cause deflection of the cathoderay beam and means for preventing a shift in the area traversed by thecathode ray beam due to a change in the alternating current axis of theapplied voltage variations, said means including a pair of unilateralconducting devices.

6. A cathode ray oscilloscope adapted to include a cathode ray tubehaving a pair of cooperating deflecting electrodes for deflecting thecathode ray beam in a predetermined plane, means including a highresistance for connecting each deflecting electrode to a point of fixedpotential, means for applying a variable wave form deflection voltagevariation in push-pull relationship to the deflecting electrodes tocause deflections of the cathode ray beam at variable intervals, andmeans including a diode associated preventing a shift in for preventinga shift deflected cathode 1 l the average position of the cathode raybeam due to a change in the alternating current axis of the deflectionvoltage variations caused by a change in wave form.

7. A cathode ray oscilloscope adapted to use a cathode ray tube having apair of deflecting electrodes to which deflection potential variationsmay be applied comprising, means for applying a predetermined staticbias potential to at least one of the electrodes relative to a point offixed potential, means for applying deflection voltage variations ofwidely different wave forms to one of the deflecting electrodes relativeto a point of fixed potential in order to cause deflection of thecathode ray beam in a predetermined plane, and means for preventing ashift in the area traversed by the deflected cathode ray beam due tochanges in applied wave form, said lastnamed means including aunilateral conducting device for producing a potential difference sothat the potential deviations of the said one deflecting electrode willprimarily extend in a predetermined direction from the static biaspotential of that electrode regal dl-ess of the wave form of the applieddeflection voltage variations.

8. A cathode ray oscilloscope in which a cathode ray tube is used whichincludes a pair of deflecting electrodes to which deflection potentialvariations are applied, means including a resistance for applying apredetermined static bias potential to one of the electrodes relative toa point of fixed potential, means for applying voltage variations ofwidely different wave forms to said one of the deflecting electrodesrelative to a point of fixed potential in order to cause dcflection ofthe cathode ray beam, and means for preventing a shift in the regiontraversed by the deflected cathode ray beam due to changes in wave formof the applied deflection voltage variations, said last-named meansincluding a unilateral conducting device connected in parallel with saidresistance for effectively producing a change in the bias potential ofthe electrode so that the potential deviations of the deflectingelectrode will always extend in a predetermined direction regardless ofthe wave form of the applied deflection voltage variations.

9. A cathode ray oscilloscope in which a cathode ray tube having a pairof deflecting electrodes may be used including means for applyingpushpull deflection voltage variations to the deflectl2 ing electrodesin which the voltage variations extend in predetermined and opposedpotential direction at the electrodes, circuit means including a pair ofresistances for individually applying a predetermined static biasedpotential to the deflecting electrodes relative to a point of fixedpotential, a pair of unilateral conducting devices each including ananode and cathode, and means for respectively connecting each of theunilateral conducting devices in parallel with one of said resistances,whereby the potential deviations of the said deflecting electrodesalways extend in a predetermined potential direction from the staticbias potential of the electrodes regardless of the wave form of theapplied deflection voltage variations.

0. A cathode ray oscilloscope in which a cathode ray tube having a pairof deflecting electrodes may be used including a source of variable waveform deflection voltage variations in which the voltage variationsextend in a predetermined potential direction, circuit means including aresistance for applying a predetermined static biased potential to oneof the deflecting electrodes relative to a point of fixed potential,means for applying the deflection voltage variations to the said onedeflecting electrode, a unilateral conducting device including an anodeand cathode, and means for connecting the unilateral conducting devicein parallel with said resistance, whereby the potential deviations ofthe said one deflecting electrode primarily extend in a predeterminedpotential direction from the static bias potential applied to thatelectrode regardless of the wave form of the applied deflection voltagevariations.

LESTER 0. SMITH.

REFERENCES CITED The following references are of record in the file oithis patent:

UNITED STATES PATENTS Number I Name Date 2,153,140 Diehl Apr. 4, 19392,173,497 Schlesinger Sept. 19, 1939 2,231,591 Pieplow Feb. 11, 19412,240,605 Bingley May 6, 1941 2,267,120 Mathes Dec. 23, 1941 2,286,894Browne et a1 June 6, 1942 2,319,139 Koch May 11, 1943

